Handheld working machines of the type concerned include brush cutters equipped with a power source formed of a gas engine. A typical example of such gas-engine-powered brush cutters is disclosed in Japanese Utility Model Application Laid-open Publication (JP-U-A) No. 03-116,751. The disclosed brush cutter includes a cartridge case associated with the gas engine and configured to hold a gas cartridge in a substantially horizontal position. In operation, a liquefied gas fuel held in the gas cartridge is supplied from a discharge nozzle of the gas cartridge to the engine for driving the engine, and the engine rotatably drives a cutting blade as a working unit to thereby perform a desired brush-cutting operation.
In the brush cutter shown in JP-U 03-116,751, the gas cartridge is disposed in a horizontal position with the discharge nozzle directed toward the cutting blade. With this arrangement, when the brush cutter is used as an unwanted grass and plants cutter, the cutting blade is disposed at a position lower than a position of the engine and, hence, the gas cartridge is disposed in a first inclined position where the discharge nozzle is directed obliquely downward. During the unwanted grass and plants cutting operation, the liquefied gas fuel held in the cartridge is supplied in the liquid phase to the engine.
Alternatively, when the brush cutter is used as a tree-branch cutter, the cutting blade is disposed at a higher position than the engine and, hence, the gas cartridge is disposed in a second inclined position where the discharge nozzle is directed obliquely upward. During the tree-branch cutting operation, the liquefied gas fuel is supplied in the gas phase to the engine. The liquefied gas fuel, as it flows out from the gas cartridge in the gas phase, allows the corresponding amount of liquefied gas to become vaporized within the gas cartridge, which will take away a great amount of heat from the gas cartridge due to latent heat of vaporization. The gas cartridge is, therefore, likely to be cooled excessively with the result that vaporization of the liquefied gas fuel is made insufficient to secure smooth feed of fuel gas to the engine even when a certain amount of liquefied gas fuel still remains inside the gas cartridge.
With the foregoing drawbacks of the prior art in view, an object of the present invention is to provide a gas-engine-powered handheld working machine having structural features enabling that a liquefied gas fuel held in a gas cartridge can be supplied in the liquid phase from a discharge nozzle of the gas cartridge to an engine with the utmost efficiency regardless of variations in the posture of the handheld working machine during use.